[Talk-us] Trunk versus motorway

Greg Troxel gdt at lexort.com
Fri Nov 30 01:36:24 UTC 2018

Bryan Housel <bhousel at gmail.com> writes:

> Can’t a motorway begin or end at an at-grade intersection though?

Certainly, and I think the question is how long does a stretch of road
that meets motorway specs have to be to be tagged motorway.  The basic
issue is that "not having at-grade intersections" is not a local
property of a road, and is really a statement about the road before and
after where one is talking about.

Assume an infinitely long road, divided, 2 lanes each way.  After a very
long time of no intersections, assume an at-grade intersection, and call
this coordinate 0, expressed in km.

Then, assume an another at-grade intersection at 0.100.  After that, at
0.110, and so on, with each being 1.1 times the previous.

By the time you get to 500 km between at-grade intersections, the
intevening roads are surely motorways.  At 100m, they surely are not.

In my view, to be tagged as motorway, the length of qualifying roadway
has to be long enough so that it feels like it is very long, as opposed
to a lucky 2 to 3-mile stretch of trunk that happens not to have any

Overall, I would throw out that if a section that meets motorway specs
isn't at least 10 miles, it's still really nice trunk, and should not be
tagged motorway.  Maybe 10 is too much and it should be 5 mi, or 10km,
or maybe it should be 20 or 25 km.   But 1-2 miles is way too short to
flip back and forth.

I have no  idea if this supports or opposes Paul in this case :-)  But
I'm guessing it supports...

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